Road or like percussive drill



Feb. 29, 1944.

F. 1., DOUGLAS ROAD 0R LIKE PERCUSSIVE DRILL Filed May 8, 1943 2 Sheets-Sheet 1 INVENTOR:

FRANK LJOUGLAS Feb. 29, 1944. F. 1. DOUGLAS ROAD 0R LIKE PERCUSSIVE DRILL' Filed May 8, 1943 2 Sheets-Sheet 2 a d I a INWINTOR: FRANK Locum .5 Hi; Arc- My:

Patented Feb. 29, 1944 UNITED ROAD R LIKE PERCUSSIVE DRILL Frank Leslie Douglas, North Gerney, near Cirencester, England Application May 8, 1943, Serial No. 486,154

In Great Britain March 19, 1942 3 Claims.

This invention relates to improvements in road or like percussive drills of the portable type generally operated by a single craftsman and comprising a pressure cylinder within which is slidably disposed a striker reciprocated therein by air pressure whereby a series of intermittent blows are imparted to a tool for road breaking, drilling or the like.

Apparatus of the described kind heretofore con structed has relied upon a supply of air pressure from an independent source for reciprocating the striker within the cylinder although selfcontained units have been. proposed in which an internal combustion engine or other prime mover has been employed for creating the necessary pneumatic pressure for actuating the striker.

The object of the present invention is to provide a road or like drill of the kind described in which the principle of the Striking action is embodied but in which the striker is given a sustained thrust subsequent to its actual striking action upon the anvil.

A percussive drill of the kind described, according to this invention, comprises a drill tool, a striker and a plunger all disposed in axial alignment, the said plunger and the said striker being disposed and adapted to reciprocate Within a cylinder, the said plunger being adapted to be reciprocated by mechanical means disposed externally of the said cylinder, the upper end of the said drill tool being freely disposed in a housing, and means being provided whereby the said striker may apply a blow to the said tool, and means for retaining an air cushion between the said striker and the said plunger so that pressure of the said plunger may be applied to the striker through the said air cushion.

Re errin to the accompanying drawings- Fig. l is sectional elevation of one form of percussive drill accordin to the invention, showing the plunger and the striker in the raised position; and

Fig. 2 is a corresponding View, but showing the plunger and the striker in the descended position.

Fig. 3 is a fragmentary sectional elevation of a modified form.

Fig. 4 is a fragmentar diagrammatic sectional elevation of a further modified form.

Referring to Figs. 1 and 2, His 2 n the lower end of which is formed a socket 52 in which the upper end it of a drill tool M is freely disposed; the drill may be provided with a collar l5 to restrict penetration of the drill end It into the socket l2. A cylinder I5 is also 'port i 1.

formed within the bod i l, above and in axial alignment with the socket E2 the said socket opening directly into the cylinder [5 through a A striker I8 is provided with a head it, in the form of a piston, disposed within the cylinder '56 and adapted to reciprocate therein in substantially air-tight contact with the internal wall of the said cylinder It. The striker l8 isalso provided with a shank 29 adapted to pass through the orifice i? into the socket l2 and make contact, when the striker is in the lower portion of the cylinder it, with the upper end It ofthe tool l4. s

A plunger 21 is also disposed within the cylinder It, above the striker l8, and is also adapted to reciprocate within the said cylinder in substantially air-tight contact with the walls of the cylinder. A. prime mover 22 is mounted on the upper end of the body I I, the said prime mover, in the form described and illustrated, being a two-stroke internal combustion engine. The cylinder 23 of the prime mover 22 is disposed in axial alignment with the cylinder i6 and socket i2, and the piston 39 is connected to the plunger M by a connecting rod 24 which passes through a port 25 in the cylinder head 25 and a sleeve 27 in anadaptor 28 connecting the prime mover 22 to the body H; the connections between the connecting rod 24 and the piston 39 and plunger 2! may be solid or free.

The cylinder I6 is divided into three separate chambers by the plunger 2! and striker head l9, an upper chamber 2% above the plunger 2!, an intermediate chamber 39 between the plunger 2| and the striker head It, and a lower chamber 3! below the striker head IS.- The upper and lower chambers 29 and 3! are connected to each other by a transfer passage 32 formed in the cylinder wall. A port 33 is disposed in the wall of the cylinder It, in a position which will be just below the plunger 21 when the said plunger is in its highest position in the cylinder, the said port leading to passages 34 and 35 in the upper end of the cylinder Hi and in the adaptor 28, respectively, the passage 35 being disposed transversely of the adaptor 28 and the sleeve 21!, and being open to atmosphere. Two circumferential grooves 36, 3'! are formed on the connecting rod the lower groove 3% in such a position that it registers with the passage 35 when the plunge 26 is in its highest position in the cylinder it, and the upper groove 3! in such a position that it registers with the passage 35 when. the plunger 2! is in its lowest position in the cylinder It. A port 38 is formed in the wall of the cylinder H5 at such a position that it is just above the upper face 0f the striker head l9 when the said striker head is in its lowest position in the cylinder l6, and just below the lower face of the striker head l9 when the striker head is in its highest position in the cylinder IS, the depth of the striker head l9 being adjusted accordingly; the port 38 allows the chambers 30 and 3| of the cylinder It to be open to atmosphere momentarily and alternately at the bottom and top of the stroke of the striker head |9, respectively.

In operation, assuming the plunger 2| to be at the top of the cylinder l6 and the striker [8 at the top of its stroke, as shown in Fig. 1, the chamber 3| will be open to atmospher through port 38, and the chamber 30 will be open to atmosphere through port 33, passages 34 and 35, and groove 36. The prime mover 22 is set in motion and the piston 39 will, through the connecting rod 24, force the plunger 2| down the cylinder IS; the port 33 will be immediately closed by the plunger 2| and the passage 35 by the connecting rod 24, and the air in the chamber 30 will be compressed and form an air cushion by means of which the downward motion of the plunger 2! applies movement to the striker head l9 and causes the striker 8 todescend in the cylinder I6 for the shank 23 to impart a blow to the upper end of the tool I4; the port 38 is also immediately closed by the striker head [9, and air in the chamber 3| is transferred by transfer passage 32 to chamber 29 so as to allow the striker l8 to descend substantially in step with the plunger 2|. The resilient blow imparted by the plunger 2| to the striker l3 through the air cushion 33 is sustained during the whole of the descent of the plunger 2| in the cylinder l6 until the port 38 is momentarily opened to the chamber 30 at the bottom of the stroke of the plunger 2|. The striker I8 will hit the tool I4 just before the striker reaches the bottom of its stroke and also just before the port 38 is opened to the chamber 30.

When the plunger 2| is at the bottom of its stroke, the groove 31 will register with the passage 35 and the port 33 will be open to the chamber 29. The plunger 2|, under the influence of the prime mover piston 39, will then commence its upward stroke; the passage 35 will again be closed by the connecting rod 24 and air in the chamber 29 will be transferred by transfer passage 32 to chamber 3| and cause the striker I8 to be raised in the cylinder IS in step with the plunger 2|, the air cushion 33 being retained. The cycle of operations will be repeated whilst the prime mover is running.

If desired, a port 4| may be provided at or near the bottom of the chamber 3|, the said port being open to atmosphere when opened by a manually controlled valve not shown; thereby, by opening the said port 40, reciprocation of the striker |8 will be prevented when the tool I4 is not required to operate, without stopping the prime mover 22. Alternatively, or in addition, a port 4! may be provided substantially medially of the length of the cylinder l5, also manually controlled by a valve not shown and also open to atmosphere when opened by said valve, so that the chamber 30 may be opened to atmosphere to prevent reciprocation of the striker when required. However, the said ports 40 and 4| may not be required; when it is not required to use the tool for a short period, the prime mover 22 may be allowed to run slowly.

In the modified form shown in Fig. 3, the port 33 is open direct to atmosphere through the wall of the cylinder l8, and the plunger 2| is provided with an upwardly extending skirt 42 of such a length that the port 33 is only opened to the chamber 29 momentarily at the bottom of the stroke of the plunger 2|. The passages 34, 35, and grooves 33, 31 shown in Figs. 1 and 2 are not provided in the form illustrated in Fig. 3.

In the form illustrated in Fig. 4 a prime mover, not shown, is disposed externally of the drill, and is connected to the body H by a flange 43 and studs 44, or any other suitable means. A spindle 45 transfers power from the prime mover to a crank 46 which, through connecting rod 41, causes the connecting rod 24 to reciprocate. The longitudinal axis of the body may be disposed at any suitable angle to the longitudinal axis of the prime mover by removing the studs 44 and rotating the body around the spindle 45 relatively to the flange 43 to the required relative positions and reinserting the studs 44; thereby, the drill may be operated horizontally or at any suitable angle whilst retaining the prime mover substantially vertical.

The drive to the spindle 45 may be transferred from a remotely located prime mover by a flexible or other driving medium.

The prime moved may be an electric motor, any type of internal combustion engine, or other prime mover.

The invention may be modified in many respects, for example, the transfer passage in the wall of the drill cylinder may be dispensed with and the striker operated in conjunction with a spring disposed between the lower face thereof and the anvil, the drill cylinder being ported on each side of the striker.

What I claim and desire to secure by Letters Patent is:

1. A percussive drill of the type described, comprising a drill tool, a striker, and a plunger all disposed in axial alignment, a cylinder within which the said plunger and the said striker are disposed and are adapted to reciprocate, mechanical means disposed externally of the cylinder and connected to said plunger to cause the said plunger to reciprocate within the cylinder, a housing within which the upper end of the drill tool is freely disposed, an extended portion of the said striker also disposed freely in said housing whereby upon reciprocation of the said striker the said extended portion may apply a blow to the said drill tool, a port in the wall of said cylinder in such position that when the said plunger is at the top of its stroke the said port is open to the cylinder space between the said plunger and the said striker and when the said plunger is at the bottom of its stroke the said port is open to the cylinder space between the said plunger and the head of the said cylinder, a passage communicating with the said port at one end and open to atmosphere at the other end, means adapted to reciprocate synchronously with the said plunger, and to control the said port and the said passage whereby when the said plunger is at the bottom of its stroke the cylinder space between the said plunger and the head of the said cylinder is open to atmosphere through said port and said passage and when the said plunger is at the top of its stroke the cylinder space between the said plunger and the said striker is open to atmosphere through said port and said passage, two further ports in the wall of said cylinder the said ports being disposed so that one of them is always open to the cylinder space between the saidplunger and the head of the said cylinder and the'other of the said ports is always open to the cylinder space between the said striker and the foot of the said cylinder, a passage communicating at each end with the said two further ports, and another passage in the wall of the said cylinder open at one end to atmosphere and having its other end providing a port positioned so as to be open to the cylinder space between the said striker and the said plunger when the said striker is at the bottom of its stroke and open to the cylinder space between the said striker and the foot of the said cylinder when the said striker is at the top of its stroke, whereby the cylinder is divided into upper, intermediate and lower cylinder spaces by the said plunger and the said striker, the said intermediate cylinder space always provides an air cushion between the said striker and the said plunger through which are cushion pressure of the said plunger on its downward stroke may be applied to the said striker the said upper and lower cylinder spaces are always in communication with each other, and the said striker is caused to reciprocate in the said cylinder in step with the said plunger.

2. A percussive drill according to claim 1 wherein the said passage which communicates with atmosphere and with the port adapted to be open to either the cylinder space between the said plunger and the said striker or the cylinder space above the said plunger according to the position of the said plunger, is intercepted by a member rigidly attached to and adapted to reciprocate with said plunger, the said member being provided with ducts at two positions whereby one of said ducts registers with said passage when the said plunger is at the top of its stroke and the other of the said ducts registers with said passage when the said plunger is at the bottom of its'stroke so that the said port is open to atmosphere when the said plunger is at the top and at the bottom of its stroke.

3. A percussive drill according to claim 1, wherein the said plunger is provided with a skirt adapted to make sliding contact with the wall of the said cylinder so as to cover, during the major portion of the stroke of the said plunger, the said port in the Wall of the said cylinder which is adapted to be open to either the cylinder space between the said plunger and the said striker or the cylinder space above the said plunger according to the position of the said plunger, and to uncover said port when the said plunger is at the top and at the bottom of its stroke whereby the said cylinder space between the said plunger and the said striker is open to atmosphere through the said port when the said plunger is at the top of its stroke and the said cylinder space above the said plunger is open to atmosphere when the said plunger is at the bottom of its stroke.

FRANK LESLIE DOUGLAS. 

